Prior art telepoint systems consist of the following elements:
1. public telepoint base stations or "birdie" stations,
2. an operating and billing system, and
3. cordless terminals.
The term "birdie" is a trade name used by DBP Telekom under which a telepoint system was offered. In this system, there are so-called private mobile units which can be used to make outgoing calls. This could also be referred to as "public cordless telephone", with the base stations assigned to the network operator/service provider, and the mobile units to the users.
An important system feature of cordless telephones, namely that "a normal mobile unit understands only its own base station", makes it clear that for telepoint service, the implementation of additional methods is important (from: Mobilfunk, Das Handbuch der mobilen Sprach-, Text- und Daten-Kommunikation, Josef Kedaj and Gunther Hentschel, Neue Mediengesellschaft Ulm mbH, February 1993, Chapter 7: Anwendungen des schnurlosen Telefons).
It is also known from the prior art that several network architectures can be used to implement the telepoint service. Three possible architectures are: standalone, overlay, and intelligent network based.
A specific feature of the telepoint service based on an intelligent network is the possibility of processing incoming calls. To this end, telephone subscribers interested in the service are assigned specific service numbers. In the standalone architecture, the base station is connected directly to the telephone network. In this telepoint service, however, only a negative selection can be made because of the large subscriber database, i.e., only subscribers without access authorization can be registered, which, in turn, has negative consequences for the security of the telepoint service.
In the overlay network architecture, the base stations are connected to the telephone network via front-end controllers. During caller validation, for example, the base station routes the information from the caller to the front-end controller and vice versa (Elektrisches Nachrichtenwesen; R. Betts, M. Martin, B. Mattlet: "Telepoint auf der Basis von ISDN and intelligenten Netzen"; Volume 64; Number 1, 1990; pp. 85-94).